Energy priority scheduling for variable voltage processors

Clock (and voltage) scheduling is an important technique to reduce energy consumption of variable-voltage processors. It is difficult, however, to achieve good results at the OS and hardware level when applications show bursty behavior. We take the approach that such applications must be made power aware and specify their future demands to a central scheduler controlling the clock speed and processor voltage. This paper describes our energy priority scheduling (EPS) heuristic that orders tasks according to how tight their deadlines are and how often tasks overlap. We schedule low-priority tasks first, since they can be easily preempted to accommodate for high-priority tasks later. The EPS heuristic does not always yield the optimal schedule, but has low complexity and can be used as an incremental on-line algorithm. We implemented EPS on a StrongARM-based variable-voltage platform. Measurements show that EPS reduces energy consumption with 50% for a bursty video decoding application without missing any frame deadlines.